Conversion of hydrocarbons



June 12, 1956 J. c. KREJCI CONVERSION OF HYDROCARBONS 2 Sheets-Sheet l Filed June 11. 1955 lll INVENTOR. J. C. KREJCI ATTORNEYS June 12, 1956 J. c. KREJcl CONVERSION oF HYnRocARBoNs Filed June 11, 1953 OGOOO'O OVOOO'O OSOOO'O OZOOO'O OIOOO O 1 J. Y B

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CONVERSION F HYDROCARBNS Joseph C. Kreici, Phillips, Tex., assignor to Phillips Petroleum Company, a corporation of Deiaware Application June 11, 1953, Serial No. 360,956

19 Claims. (Cl. 260-679) This invention relates to the pyrolysis of hydrocarbons. In one aspect this invention relates to the manufacture of unsaturated hydrocarbons. In another aspect the invention relates to the production of aromatic hydrocarbons. In another aspect the invention relates to the production of olefins. In still another aspect the invention relates to the production of acetylene. In another aspect the invention relates to the cracking of hydrocarbons at higher temperatures and shorter reaction times than have heretofore been possible.

This application is a continuation-in-part of my copending application Serial Number 106,191, tiled July 22, 1949, and now abandoned.

A number of thermal methods have been proposed for the manufacture of oletins, acetylenes, and aromatic hydrocarbons, and certain valuable by-product parafln hydrocarbons from various hydrocarbon cracking stocks. Many of these proposed methods involve thermally treating the hydrocarbon stock in cracking-tubes disposed in a conventional gas-fired furnace. Normally, these processes are conducted at temperatures below about l300 F., in View of the operating diliiculties that occur at higher temperatures as a result of excessive carbon deposition, and cracking-tube failure. Such a temperature limitation is disadvantageous from the standpoint of producing such valuable unsaturated compounds as ethylene and acetylene, in high yield, as indicated by equilibrium considerations which show that temperatures above 1300 F., are highly desirable for the production of these compounds. Prior art processes have been unable to take advantage of the higher temperatures which have been shown favorable for the production of high yields of acetylene and other unsaturates. This is particularly true of those processes using tube coil reactors wherein high temperatures have formerly been impossible because of the concomitant deposition of coke. Prior art processes have also been inherently unable to provide very short reaction times which are necessary to facilitate the survival of acetylene, for example, once acetylene has been formed.

This invention is concerned with a process for pyrolyzing hydrocarbon stocks at temperatures in the preferred range 1300 to 3500" F., wherein carbon deposition is greatly minimized or entirely eliminated, and light oletin hydrocarbons, particularly ethylene and propylene, and acetylene are produced and recovered in high yield, together with aromatic hydrocarbons, higher molecular weight olefins, valuable parains and the like, as byproducts. Another feature of the invention is that extremely high daily throughputs and production rates are feasible in relatively small reactors.

Another feature of the invention is that extremely short reaction times, in some cases less than 0.001 second, are feasible. According to this invention there is provided a process which comprises passing a hydrocarbon feed axially into a precombustion zone; passing a combustible mixture comprising a fuel and an oxidant tangentially.,

into said precombustion zone; effecting combustion of 2,750,434 Fatented June 12, 1956 said combustible mixture to form combustion gas to be contacted with said hydrocarbon feed; passing said hydrocarbon feed, initially surrounded by a helically moving annularblanket of said combustion gases, into a reaction zone; therein reacting said hydrocarbon feed by virtue of heat imparted thereto by said combustion gases, to form, predominantly, unsaturated hydrocarbons, and recovering said unsaturated hydrocarbons.

In accordance with my invention, a hydrocarbon stock is pyrolyzed under specific conditions in a tangential burner reactor, described hereafter, to form pyrolysis product at temperatures higher and reaction times lower than those employed in ordinary tube-cracking processes. A combustible fuel mixture is burned to maintain a steady flame in a tangential burner-reactor, and resulting hot combustion gas is contacted in direct heat exchange relation with a selected hydrocarbon stock, to heat same to a pyrolysis temperature whereby valuable pyrolysis products are formed.

In the practice of this invention unsaturated aliphatic hydrocarbons, aromatic hydrocarbons and certain by product parahin hydrocarbons are produced by hydrocarbon pyrolysis in a tangential burner-reactor, or furnace system, containing two cylindrical sections, one of which may be termed a precombustion section, and the other, a reaction section. These two sections are adjacent each other and coaxial, and are preferably disposed horizontally. The combustion section is positioned upstream frorn the reaction section and ordinarily has a shorter length and a larger diameter as compared to the adjacently disposed reaction section. One embodiment of this invention comprises passing a combustible fuel mixture into the precombustion chamber in a direction tangential to its inner side wall, while at the same time axially introducing the hydrocarbon reactant into the combustion section, alone or with additional oxygen. The tangentially introduced fuel is burned, upon or prior to entrance into the combustion chamber, and the resulting hot total product of burning, i. e. combustion gas, comes into contact and in direct heat exchange relation with theaxially introduced hydrocarbon charge. The tangentially added mixture is injected into the combustion section at a sufficiently high velocity to cause combustion gas formed therein to flow spirally inward, and substantially helically downstream through the reaction section. Combustion gas thus formed, together with axially introduced hydrocarbon, is passed into the reaction section in an initial state of annular separation. The helically moving combustion gas forms a gas blanket adjacent the reactor wall, and in this manner, direct contact of the hydrocarbon reactants with the reaction chamber walls is substantially prevented, and carbon deposition is greatly reduced.

In my U. S. Patent 2,377,245, I disclose a process for converting hydrocarbons to acetylene in a cylindrical reaction chamber in a manner similar to the method briefly described above, except that the combustion and pyrolysis take place in one cylindrical chamber. My present invention, however, provides for conducting such a process in a tangential burner reactor having a combustion section and a reaction section of different dimensions already briefly described. In the practice of my present invention as compared with my process disclosed in U. S. 2,377,245, I am able to effect a higher volume of production relative to the volumetric reactor capacity Without encountering difliculty in maintaining the flame. I can obtain higher concentrations of acetylenes and olefins in the effluent gases, resulting in simple product recovery and small recovery equipment. Furthermore, I obtain fast reaction as a result of the burning taking place before contact with the axial reactant gases to provide higher combustion temperatures at the time of contact with the axial feed.`

Also, the present process provides for utilizing tangential fuel hydrocarbons of poorer combustion characteristics than the usual process, as the flame is more easily maintained in this apparatus.

The accompanying diagrammatic drawing illustrates one form of tangential reactor apparatus that may be employed in the practice of my invention, together with associated equipment. However, it is to be understood that various modifications of the illustrated process and apparatus may be made and still remain within the scope of my invention.

Figure 1 includes a transverse sectional view of a furnace embodying my invention, taken on the line 1 1 of Figure 2, together with a diagrammatic ilow sheet illustrating other apparatus used in practicing a preferred embodiment of this invention. Figure 2 is a cross-sectional view of the same furnace taken on the line 2 2 of Figure 1.

Referring to Figure l, elongated reaction section is lined with highly refractory material 11, such as corundum brick, silica brick, mullite brick, Zirconia brick, sillimanite brick, or other similar suitable materials resistant to high temperatures developed therein. Upstream from, and adjacent section 10, is combustion section 12, coaxial with section 10. Section 12 is also lined with lining material 11 such as already described, which can be the same as, or different from, the lining of section 10. Lined sections 10 and 12 are surrounded by a layer of insulating material 13 and the Whole is contained in an outer steel shell 14. Combustion chamber 12 can have a relatively large diameter in comparison to its length while the reverse is true of reaction section 10.

At the upstream, or inlet end of combustion section 12, is feed inlet conduit 21 arranged axially so that hydrocarbon feed introduced therethrough will pass axially through both sections 12 and 1%. Surrounding feed conduit 21 is a coaxial, larger conduit or oxygen inlet 22. The arrangement of conduits 2li and 22 defines an annular space through which oxygen, or a suitable oxygencontaining gas, may be axially passed into chamber 12. Oxygen when passed through that annular space serves to cool the inner end of conduit 21; if any carbon deposits thereon, oxygen thus introduced will support combustion to burn the carbon free. Diluted oxygen, steam, air or a mixture thereof may also be introduced into this annulus.

Referring to Figure 2, in combustion section 12 are arranged inlets 23 which are so disposed that gas or oil, together With steam, as desired, may be passed therethrough into combustion section 12 in a direction tangent to its cylindrical inner side wall and preferably perpendicular to the longitudinal axis of section 12. Each tangential gas inlet 23 may consist of a conduit 24 joining a larger conduit or tunnel 26 which terminates as an opening into chamber 12. An inlet pipe 27 extends part way into conduit 24. Most of the tangentially introduced gas is burned in tunnels 26. Cooling assembly 18 downstream from reaction section 1li is preferably coaxial therewith and consists of water jacket 2S, water spray 29, Water inlet conduit 31 to jacket 28, space 32 in which cooling water is passed through jacket 23, Water outlet 33 from jacket 28, and water inlet 34 to sprayer nozzle 25.

In one embodiment of my invention a combustible mixture of natural gas and oxygen containing an amount of oxygen within the range of from 70 to 90 volume percent of the theoretical amount for complete burning, is preheated and charged to tangential burner 23. This can be done by introducing natural gas from line 4l through line 43 in admixture with oxygen introduced from line 47 through 4S, into preheater 42 wherein the resulting natural gas and oxygen is preheated to the desired temperature. Preheated natural gas-oxygen is withdrawn from preheater 42 through line 51 and introduced tangentially into combustion section 12 through line 27.

If it is desired to dispense with all preheating, natural gas from line 41 and oxygen from line 47 can be respectively introduced to line 27 `Vfrom line 44 and from line 49. In some instances it is advisable to preheat a selected portion of either or of both the natural gas and oxygen, and to introduce preheated gases into line 27 from preheater 42, together with oxygen and/or methane, passed around preheater 42, through lines 49 and/ or 44 respectively. Tangentially introduced natural gas is burned in tunnels 26. The combustion gas produced travels spirally toward the center within combustion section 12, and then helically through elongated section 10 as a protective gas blanket adjacent the Wall thereof. Although in this specific instance of operation, an amount of oxygen within the limits of 70 to 90 percent of theoretical for cornplete burning, is added tangentially with the natural gas, it is advisable in some instances to completely burn natural gas tangentially added, particularly when higher operating temperatures are sought for the purpose of forming acetylene in selectively high yields. When the amount of oxygen is from 70 to 9G percent, or more, of the stoichiometric requirement for complete combustion, steam tempering of the tangential gas, as herein described, is preferred.

Propane and any required oxygen are preheated and introduced axially into combustion section 12. This may be done by preheating propane from line 56 in preheater 57, and passing the resulting preheated gas through lines 5S, 59 and 21, axially into the reaction system. If it is desired to dispense with propane preheating, propane from line 56 may be passed around preheater 57 through line 54 into lines 59 and 21. lf desired, preheated gas from line 58 may be admixed with propane from line 54 in any desired proportion. When introducing oxygen into the reaction system axially, oxygen from line 61 is preheated in preheater 62 and the resulting preheated oxygen is passed through lines 63 and 2li and conduit 22 into chamber 12. If it is desired to dispense With oxygen preheating, oxygen from line 61 may be passed around preheater 62 through line 64 into line 2h. Preheated oxygen from line 63 may be admixed with oxygen from line 64 in any desired proportion. it is sometimes desirable to charge a mixture of oxygen and propane through axial conduit 21 in which case oxygen from either of, or both, lines 63 and 64 may be passed through line 66 into lines 59 and 21 and on into chamber 12.

The amount of preheat for the reactants herein is limited; in the case of an oxygen stream, by its reactivity with other reactants; in the case of an oxygen-hydrocarbon mixture, by the tendency of that mixture to preignite; and in the case of a hydrocarbon, by the tendency of the hydrocarbon to thermally decompose to form undesirable decomposition products, particularly carbon. For that reason it is usually desirable to limit the preheat of the oxygen-containing feed streams discussed herein, to a temperature usually not greater than about 1000 F. When preheating hydrocarbon alone, a preheat temperature Within the range of 800 to l500 F., may be advantageously employed, the speciiic temperature depending on the thermal stability of the specic hydrocarbon. However, limited cracking of the reactant hydrocarbon, e. g. at temperatures above 900 F., can be advantageously practiced so long as undesirably large amounts of carbon are not formed on preheater walls.

The burning taking place in tunnels 26 serves as a source of heat for the pyrolysis reaction taking place in the system, and is regulated by adjusting the amount of natural gas burned and the mol ratio of oxygen to natural gas tangentially added. Combustion products comprise carbon dioxide, hydrogen, steam and carbon monoxide in relative amounts dependent largely upon the mol ratio of oxygen to natural gas or other fuel in the tangential feed. The axial hydrocarbon stream is prevented, by the helically moving combustion blanket, from contacting the walls of the reaction section until at least reaching a downstream portion of the reactor, and thus little chance is afforded the hydrocarbons to contact the hot walls and decompose with the formation of undesirable carbonaceous deposits. The annular or helical blanketing appears to continue through about the first 6 to l0 inches of length of the reaction section. This length represents the portion of the reactor in which carbon would deposit in the absence of any blanketing.

Product gas from section 10 is passed into cooling assembly 18 and rapidly quenched to a temperature below that at which unsaturated products of pyrolysis, particularly acetylene or ethylene or other olenic materials may pyrolyze, or decompose, which is usually a temperature below about 800 F., quickly obtained by both indirect and direct heat exchange relation of the gas product with water or other coolant. Product gas from cooling assembly 28 is then conducted through line 19 to purification zone 36 comprising product separation and recovery equipment, such as distillation, solvent extraction, absorption, settling and the like, not individually illustrated, suitable for lseparating product gases and carbonaceous materials present in the eiiiuent gas stream from cooling assembly 28. As an example of various separation and recovery steps tht-.t may be utilized in separation zone 36, all of which are well known to those -skilled in the are, are charcoal adsorption, mineral oil absorption, conventional distillation equipment, and solvent extraction, particularly acetone extraction for acetylene recovery, and the like. Steam present in the gas entering zone 36 is separated therein preferably by condensation, and withdrawn as water through line 45. Other products separated in zone 36 may be acetylene withdrawn through line 38, ethylene kwithdrawn through 39, other olefin product withdrawn through line 37, aromatic hydrocarbons withdrawn through line 20, heavier hydrocarbon product withdrawn through line 50, and by-product parafn hydrocarbons withdrawn through line 46.

For convenience and clarity certain apparatus, such asV pumps, surge tanks, accumulatore, valves, etc., have not been shown in the drawing. Obviously, such conventional equipment can be assembled to practice the present invention without departing from the scope of the invention.

Feed stocks advantageously utilized in the process of my invention are, generally, normally gaseous hydrocarbons, naphthas boiling below about 600 F., and gas oils boiling from 450-900 F., or mixtures of these hydrocarbons, although heavier hydrocarbons may be employed, when desired. Although I may employ an aromatic hydrocarbon-containing feed, my process is particularly well applied to the conversion of parafn hydrocarbon stocks; I obtain higher yields of desired pyrolysis product when pyrolyzing predominantly paraiin hydrocarbon stocks than when pyrolyzing predominantly aromatic hydrocarbon stocks. Thus, according to this invention feed stocks that may be employed include methane, ethane, propane, butane, pentane, naphtha, kerosene, and gas oils.

In general, the conditions of reaction time and temperature employed in the process of this invention are those temperatures and times at `which the predominant reaction is cracking or pyrolysis to form unsaturated and aromatic hydrocarbons as the predominant reaction products as distinguished from the formation of carbon black and the formation primarily of such product gases as hydrogen and carbon monoxide as the chief products of the process. Broadly, the preferred temperature range is from 1300 to 3500 F., and the reaction time is ordinarily not greater than a few seconds. However, it has been found that reaction temperature and reaction time are inseparably interrelated. Thus, at a given temperature, reaction times within a certain general range are permissible; whereas, at higher temperatures reaction times within a given range, but much lower than at lower ternperatures, are used. Broadly, the relation between temperature and time has been found to be in accordance with equations set forth subsequently. Thus, within the broad scope of the invention, the maximum time of reaction has been found to be related to the reaction temperature according to the following equation:

wherein t is reaction time expressed in seconds and T is reaction temperature expressed in degrees Rankine.

Generally, the lower limit of reaction time for any given reaction temperature will be in accordance with the following equation:

wherein t and T have the dimensions set forth above. It has been found, in accordance with this invention, that reaction times as low as 0.6 millisecond can be used at a reaction temperature of 2590" F. However, it has been found that reaction times substantially lower than this value and lower than those expressed in Equation 2 above can be used in .some cases.

Generally, the specific reaction temperature used will depend upon the product desired and the feed hydrocarbon to be reacted. Generally, a preferred range of reaction temperature for the predominant production of olen hydrocarbons has been found to be in the range 1300 to l900 F., and a preferred temperature range for the production of acetylene has been found to be from 1900 to 3500 F. However, the olefin production range and the acetylene production range overlap to some extent, and it has been found desirable, in some cases, according to this invention, to operate in a temperature range of 1700 to 2300 F., when it is desired to produce substantial yields of oleiins and acetylene simultaneously.

When it is desired to produce acetylene from ethane or propane, the preferred maximum reaction time to be used within the temperature ranges already disclosed, has been found to be in accordance with the following equation:

1 12,650 10g 5.34 T (a) The lower limit of contact time for the production of acetylene from ethane or propane has been found to be in accordance with the following equation:

When it is desired to produce acetylene from hydrocarbons in the molecular weight range from butane to naphtha, the upper reaction time limit has been found to be in accordance with the following equation:

The lower limit of reaction time has been found to be in accordance with the following equation:

10g (iD-:aes-L@ (e) When the production of olefns from ethane or propane is desired the maximum reaction time has been found to be in accordance with the following equation:

The minimum reaction time has been found to be in accordance with the following equation:

When it is desired to produce olens from hydrocarbons in the molecular weight range from butane to naphtha, the maximum reaction time is obtained in accordance with the following equation:

7 The lower limit of reaction time is according to the following equation:

Thus, when it is desired to produce oletns from hydrocarbons ranging in molecular weight from ethane to hydrocarbons having an upper boiling point of about 900 F., the maximum reaction time is obtained in accordance with the relation and the minimum time is obtained in accordance with the following equation:

My invention provides for utilization of temperatures much higher than the conventional temperature levels provided by well known tube-cracking processes, at much shorter contact times and for minimizing loss of pyrolysis reactants to undesirable side reactions, particularly to carbon formation. My invention provides, therefore, for the utilization of feed stocks selected from within a Wide boiling range, in the manufacture of olefins, acetylenes, and aromatic hydrocarbons.

It is to be understood that although my invention may be utilized without use of the above general inter-relation and various related inter-relations to be discussed hereafter, higher yields of desired product and a concommitantly lower amount of undesirable side reaction are obtained when within limits defined by these equations, than when conducting such a pyrolysis independently of such an inter-relation.

As determined in accordance with such inter-relations of my invention, hydrocarbons may be pyrolyzed to produce a particular pyrolysis product in high yield over a specific range of reaction times, at a given temperature level or, at a given contact time over a specific temperature range.

The general form of the foregoing equations is derived as follows:

t Og a-:e

(13) (lst order rate equation) where a=initial amount of conversion stock x=amount converted k=rate constant t=time of reaction Subtracting log C4 (a constant) from both sides,

In the use of these interrelations, I may select a specic temperature level and determine the lower and upper limits of a range of contact time in which a selected pyrolysis feed stock may be converted to the desired unsaturate product. Accordingly, I may substitute the desired temperature level in the proper pair of interrelations and thus determine two values for t, which limit the time range in which acetylene or olefin is most eiliciently and economically produced at that temperature level.

I may, therefore, determine an optimum range of contact time at a specific temperature level for any embodiment of the process of this invention, by substitution of the specified temperature value in the appropriate interrelatiou. If desired, a constant value for contact time may be substituted in a pair of interrelations of the type discussed herein, and the appropriate temperature range may be determined.

Pyrolysis temperatures can be measured at any desired point in the reaction system. However, I prefer usually to measure these temperatures at a point in the forepart of the reaction zone, generally by means of an optical pyrometer sighted on the reactor wall.

Those skilled in the art will recognize that a graphic plot of any of the pairs of the foregoing equations interrelating maximum and minimum reaction time to temperature will result in an area which will define the optimum operating limits of temperature and contact time according to the present invention. In Figure 3 of the drawings Equations l and 2 have been plotted to illustrate this point. In Figure 3 values of log of have been plotted on the vertical axis. (The logarithm used in the foregoing equations is a base l0 logarithm.) On the horizontal axis is plotted the reciprocal of temperature, temperature being expressed in degrees Rankine. Thus, the line AB represents a preferred upper temperature limit of 3500 F. Line CD represents a lower temperature limit of 1300" F. Line AD represents the Variation of maximum reaction time between the upper and the lower temperature limits. Line BC represents the variation of minimum reaction time within the maximum and minimum temperature limits.

Thus, when operating in accordance with this invention, one skilled in the art can determine the optimum temperature and the Optimum reaction time by calculation from the foregoing equations or by reference toa plot similar to that shown in Figure 3.

The dimensions of specific tangential burner reactors are speci'cally described in the examples hereinbelow. However, the ratio of the diameter of the enlarged combustion section to that of the reaction section is preferably between 1.511 and 4:1, and the ratio of the diameter to length of the combustion section is preferably between about 6:1 and 1:1. The reaction zone is of such length as to provide the desired reaction time to effect the conversion.

Generally, optimum results are obtained when the tangential feed contains fuel and oxygen in the stoichiometric ratio with respect to each other. However, from 50 to per cent of the amount of oxygen theoretically required for complete combustion of the tangentially introduced fuel produces satisfactory results. Addition of sufficient steam to the tangentially introduced gas to control the reaction temperature within the desired limits is often preferred, especially when the ratio of oxygen to fuel is such that extremely high temperatures are obtained on combustion, in order to prevent damage to the reactor. A tangentially introduced mixture containing less than sufficient oxygen for complete combustion, e. g., 70 to 90 per cent of the stoichiometric amount, is optimum for the prevention of carbon deposition in the reactor and for avoiding loss of axially introduced feed by oxidation. However, mixtures rich in oxygen can be used without obtaining carbon deposition.

Although air may be used in the burning in the combustion section, it is preferred that oxygen of commercial grade purity be used, i. e., from 90 to 95 per cent oxygen purity, in order to prevent dilution of the pyrolysis products with nitrogen, and to simplify product recovery.

was 194 pounds. Based on the volume of the reaction section only, the production was 22.4 pounds per cubic foot per hour.

EXAMPLE 2 Propane was pyrolyzed in the apparatus of Example 1. Two tangential burners were employed and were spaced 180 apart. The tangential feed mixture was air and natural gas of approximate compositions, the results of which are summarized in the tabulation hereinbelow:

Run Propane Propane Tangential Air-Nat. Reactor Yleld Welght percent based on Axial Feed No Re, Prceleat, irIIialge, Gas Vol. Temp.,

- Ratio F H. on. om. 01H. ogn. Benzene 40 300 700 100, 000 14 7. 05 18. 85 27. 1 11. 9 0. 0 4. 2 41 350 700 100, 000 14 2, O95 5. 60 22. 87 21. 6 27. 2 0. 0 3. 72 42 400 700 100, 000 14 1, 97() 5. 02 25. 67 15. 89 38. 5 0. 0 3. 24 45 550 700 100, 000 14 1, 906 3. 9S 22. 10 8. 67 31. 20 6. 66 1. 98 47 700 700 100, 000 14 1, 840 2. 87 9. 60 6. 33 27. 7. 02 0. 89 48 500 700 10i), 000 7. 5 1, 788 4. 55 18. 30 7. 84 29. 25 15. 70 1. 41 49 400 700 100, 000 7. 5 1, 850 5. 77 31. 30 10. 20 42. 10 3. 71 2. 47

Further, in accordance with this invention, it has been found that when relatively pure oxygen is used as the oxidant in the tangentially introduced combustible mixture, it is desirable to introduce along with the fuel and the oxidant an inert gas or vapor, preferably steam, in order to reduce the extremely high flame temperature obtained. Although inert gases such as nitrogen can be used as the tempering gas to reduce the iame temperature, it is preferred to use steam, since steam is readily removable by condensation from the gaseous products of reaction and does not undesirably dilute said products. The volume ratio of steam to oxygen may be varied within broad limits. However, it has been found desirable to use a volume ratio in the range 1:1 to 5:1, a 3:1 ratio prcducing very desirable results; however, it should be understood that steam to oxygen ratios beyond these limits can be used.

The advantages of this invention are illustrated by the following examples. The reactants and their proportions and other specific ingredients are presented as being typical and should not be construed to limit the invention unduly.

EXAMPLE 1 Natural gas having the following composition was charged to a tangential burner reactor both tangentially and axially. The burner reactor had a combustion sec*- tion 33 inches in diameter and was 12 inches in length and the reaction section was 12 inches in diameter and 11 feet in length. Tangentially added natural gas Was burned in the combustion chamber and axially added gas was introduced without supplemental oxygen. Data summarizing this run are tabulated as follows. The composition of the residue gas was as follows:

Component: Mole per cent N2 '8.45 CH4 81.7 C21-Ie 5.84 C3Hs 3.11 C4H1o 0.87 C5| 0.03

Operating data Temperature:

Combustion section F 2822 Reaction section F 2246 Contact time seconds 0.043

Pressure Atmospheric Natural gas feed, C. F. H.:

Axial 30,000 Tangential 7,700 Tangential air, C. F. H 100,000

Axial natural gas preheat F 1,000

The eluent gas on a dry basis contained 2.14 Volume per cent acetylene. The production of acetylene per hour From these data, it is seen that higher yields of ethylene are favored when employing a hydrocarbon-rich tangential burner feed. It may also be seen that the lower reaction temperatures favor production of olens rather than acetylene.

Carbon deposition within the reactor was negligible with the rich burner feed, but it did show up to a slight extent in runs with excess air charged to the tangential burners.

EXAMPLE 3 A petroleum naphtha characterized by the following inspection data was charged to the tangential reactor of Example 2 during runs Nos. 59, 60, 6l, and 62.

API 47.6

Anline No F 123 ASTM Dist.:

IBP F 134 5% F 195 10% F 227 20% F 268 30% F 318 40% F 356 50% F '388 60% F 414 70% F 440 F 461 F 483 F 499 EP 515 Rec per cent 98 A petroleum naphtha characterized by the following inspection data was charged to the tangential reactor of Example 2 during runs Nos. 51, 25, 24, and 23.

API 51.5 NPA color -l ASTM Dist.:

IBP F 176 10% F 245 20% F 267 30% F 287 40% F 306 50% F 327 60% F 347 70% F 374 80% F 401 90% F 430 EP 471 Rec per cent 97.5 Carbon residue Nil Aniline No F 134.8 Refractive index at 20 C 1.4285 Pour point F -70 SUV at F 29.1

12 per cent propane, together with smaller amounts of hydrogen sulde, carbon dioxide, hydrogen, and butanes. The tangentially introduced fuel was natural gas and the oxidant was oxygen.

The reactor used according to this example was designed substantially as shown in Figures 1 and 2. The precombustion section was 11 inches in diameter and 4 inches in length. The reaction section Was 3 inches in diameter and 25 inches in length.

This example also illustrates another feature of my invention, namely, that the axially introduced hydrocarbon feed can be preheated to such a temperature, prior to Run Number 62 61 60 59 51 25 24 23 Axial Charge Rate, Ga1./Hr 425 425 425 425 375 325 250 150 Tangential Air Rete, C. F. EL 62,500 75, 000 87, 500 100,000 100,000 100, 000 100, 000 100,000 Tangential Fuel Gas Rate, C. F. H 8, 3 10, 000 11, 650 13, 500 13, 500 13, 500 13, 500 13, 500 Jacket Air Rate, C. F. H None None None None None 4, 000 4, 000 4,000 Axial Charge Preheat, F 600 610 600 575 665 605 605 720 Air/Gas Volume Ratio (Tangentia 7. 5 7. 5 7. 5 7.4 7.4 7.4 7.4 7. 4 Reaction Chamber Temp., l, 495 l, 545 1, 605 1, 650 1, 735 l, 840 1, 930 2, 240 Reaction Time, Sec 0.092 0.076 0. 063 0.056 0.054 0.050 0.049 0.044

PRODUCT DISTRIBUTION, WT. PERCENT OF CHARGE Component: (a) (a) (b) (b) Hydrogen 1. 90 2.17 2. 65 2. 80

Methane 9. 22 10. 88 12. 38 11. 99

Acetylene 2. 63 4. 10 5. 23 5. 12

Ethylene 16. 37 20. 11 25. 10 29. 55

Ethane 1. 30 2. 99 3. 13 1. 51

Methylacetylene 0. 52 0. 94 0. 72 1. 59

Propylene 6. 17 8. 88 9. 47 8. 83

Propane 0. 49 0. 99 0. 70 0. 42

Dimethylacetylene 0. 61 0. 43 0. 78 0. 72

Butadieue 2. 46 3. 07 4. 71 5 67 Butylenes. 2. 90 3. 24 3.12

Butanes 0.53 0.59 (l. 48 0.08

Benzene- 2.89 4. 17 4. 31 5. 92

05+ (From Charcoal Adsorber 4. 78 2.04 1. 63 0. 50

Tar Trap Liquid 31. 29 18.15 8.25 7. 17

n No carbon in reaction zone.

b Ring o carbon at inlet of reaction zone. No carbon.

d Some carbon in reaction zone.

PRODUCT CONCENTRATION, MOL PER CENT OF WATER-FREE EFFLUENT Component:

Carbon Dioxide 4. 19 4. 26 4. 27 4. 76 3. 91

Carbon Monoxide 7.61 7. 59 8. 31 7. 30 9. 56

Nitrogen 55. 68 56. 47 55. 30 57. 92 59. 27

Hydrogen- 10. 99 10. 59 10. 86 10. 85 11. 18

Methane 6. 70 6. 68 6. 38 5. 66 5. 42

Acetylene 1. 18 1. 55 1. 66 1. 49 1. 37

Ethylene 6. S0 7. 06 7. 40 7. 98 5. 99

hane 0. 84 0. 98 0. 86 0. 38 0. 79

hethylacetylene 0. 15 0. 23 0. 15 0. 30 0. 14

Propylene 1. 71 1. 95 1. 86 1. 59 1. 13

Propane 0.13 0. 22 0.13 0.07 0.09

Dimethylacetylene 0. 13 0. 08 0. 12 0. 10 0. 07

Butadiene 0. 53 0. 5G 0.72 0 78 0 El 1. 6 0. 63 0. 85 o. 2s o. 2s o. 39 0.81 0. 54 0. 76 0. 20 0. 2l

l Total acetylene by Orsat.

2 Total olefms by Orsat.

EXAMPLE 4 70 introduction into the precombustion Zone, that a limited prising 66 per cent ethane, 25 per cent methane, and 7 V75 amount of cracking of the said feed occurs. In this example preheating and precracking were obtained by the use of two coil preheaters in series. The coil diameter was 1 inch and the total coil length was 200 feet. The results obtained are shown in the following table:

Cracking of ethane to produce acetylene Run No 1 2 3 4 5 Axial Feed C, F. H 1, 895 1, 895 1, 515 1, 705 1,895 Tang. Gas, O. F. H 1, 500 1, 500 1, 500 1, 500 1, 500 Tang. Oxygen, C. F. B.' 3, 000 3, 000 3, 000 3, 000 3, 000 Tang. Steam, C. F. H 7, 500 7, 500 7, 500 7, 500 7, 500 Axial, Preheat, F 1, 450 1, 450 l, 450 1, 450 Axial Precrack, VoLpercent olefins 22. 6 27. 8 Reaction Temp., F 2, 700 2, 600 2, 600 2, 600 Reaction Time, seconds 0. 0031 0. 0035 0.0035 .0034 Orsat Gas analysis, volume percent, dry basis' C2 2. 10. 42 l1. 1 11.28 12.53 12.32 9.84 4. 3 5. 20 5. 22 5. 68 1.25 1. 3 0.76 1.78 44. 59 47. 4 47. 60 47. G2 8 12. 96 13. 8 15.07 13. 18 17. 43 18. 6 17. 69 17. 00 0.21 0.4 0.10 0.00 N 3. 30 3. 1 2. 30 2. 67 Acetylene d,

Axial Feed. 40. 5 48. 2 48. 1 49. 9 Acetylene Prodn. 1, 350 1, 385 1, 690

The foregoing data show that acetylene yields as high as 49.9 per cent, based on the Weight of the axial feed, can be obtained by the use of the present invention. This is believed to be an unusually high acetylene yield for a cracking process. Furthermore it will be noted that production rates as high as 1690 pounds of acetylene per day were obtained. This is believed to be an unusually high throughput When it is considered that the reactor used in this example was only 3 inches in diameter and inches in length.

EXAMPLE 5 This example illustrates the production of acetylene from normal butane according to this invention and utilizing a reactor of the type described in the preceding example. In this example no steam tempering was used in the tangentially introduced gas and no precracking of the axially introduced hydrocarbon feed was utilized. The tangentially introduced fuel was residue gas. The results are shown in the following table.

Cracking of butane to produce acetylene at low reaction time Run N o.- 1 2 Axial Feed, Butane lb./hr 293 304 Axial Feed, Oxygen, O. F. EL.-- 2,000 2, 500 Tangential Feed, Residue Gas, C. 3,850 3, 850 Tangential Feed, Oxygen, C F H 4, 150 4, 160 Axial Butene Preheat, F, 600 600 Length Reactlon Sectlon 7 7 2, 730 2, 590 0.7 0.6

6. 06 6. 68 6. 54 5. 16 2. 50 0. 99 44. 32 46. 00 32. 51 34. 20 4. 54 4. 59 2. 20 2.17 O 1. 83 0. 21 02H1 Yield Wt. Percent of Butane 27. 5 30. 7 C2H2 Prod'n. lb./day 1, 930 2, 240

The foregoing data show that high yields of actylene can be produced from butane according to this invention at very high temperatures and very low reaction times.

EXAMPLE 6 This example illustrates the conversion of butane to acetylene and the use of steam tempering of the tangentially introduced gas according to this invention. In runs l and 2 in the following table a reactor having a 3 inch diameter reaction section and Similar in .design to that in examples 4 and 5 was used. In run 3 in the table a 12 inch diameter reactor of the type disclosed in Example lfwas used. The results are shown in the following table.

Butane cracklng with Steam temperlng Run No 1 2 3 Reactor diameter -mch 3-inch 12-inch Axial Feed:

Butane, lb./hr 107 158 Butane, gaL/lir 354 Tangential Feed:

Residue gas, C. F. H 1, 250 1, 500 13, 570 Oxygen, C. F H 2,500 3,000 Air, c. F. 190, 000 Steam, C. F. H 7, 500 7, 500 Axial Butane Preheat, F 1, 300 1, 400 700 Reaction temperature, F.. 2, 550 2, 600 2, 450 Contact time, milliseconds 3. 9 3. 2 22 Orsat Analysis, percent by volume (dry The foregoing data illustrate the high yields of acetylene from butane obtainable according to the process of this invention. The acetylene production rate was 1510 pounds per v24 hours.

EXAMPLE 7 This example illustrates the production of acetlylene from natural gas (chieily methane) according to this in vention. The reactor used in this example was similar to that used in Example 4 except that the effective length of the reaction section was made variable by the use of a movable quench pipe which allowed the introduction of a water quench at any desired point in the reactor.

Natural gas was used as the hydrocarbon feed and also as the tangentially introduced fuel.v Oxygen was used as the tangentially introduced oxidant. In addition some oxygen was used as a component of the axially introduced feed. The results are shown in the following table.

Production of acetylene froml natural gas Run 1 2 3 4 Tanential feed, C. F. H.:

2,114 1, sse

2, 114 1, sse 1, 886

Natural Gas Length of reaction zone, in Reaction temperature, F. Reaction time, see C2H2 concentration in effluent (dry basis), vol. percent 02H1 yield, Wt. percent axial natural gas CaHz production, lb./24 hr In this example the axially introduced natural gas was preheated to 600 F. prior to introduction into the reactor.

The foregoing data show the high temperatures, short contact times and high yields of acetylene and high production rates of acetylene obtainable according to the process of this invention.

In respect of the 3-inch diameter reactor discussed in the foregoing examples, the reaction section of the reactor can be considered substantially adiabatic, the reactions occurring therein being exothermic. The reaction temperature decreased in the direction of flow. When the length of the reaction section was 25 inches, the temperature in the upstream third was very high. That of an adjacent downstream portion decreased rapidly in the direction of ilow. In the next adjacent portion downstream, the temperature decreased more slowly in the direction of ilow. Where the eifective reaction section was 25 inches long, the reaction temperatures in the examples were measured immediately downstream from l the portion of the most rapid temperature drop. Where the length of the reaction section was 7 inches, there was no portion of extremely rapid temperature drop, and the temperatures in the examples correspond to the temperatures in the hottest portion of the reactor which was inches in length.

It was found, in accordance With this invention, that a somewhat lower reaction time was optimum when the 3 inch diameter reactor of the foregoing examples was used than when the 12 inch diameter reactor was used.

Variation and modifications are possible within the scope of the disclosure and the claims to this invention, the essence of which is that there has been provided a process which comprises passing hydrocarbon feed axially into a precombustion zone; passing a combustible mixture comprising a fuel and an oxidant tangentially into said precombustion zone; effecting combustion of said combustible mixture to form combustion gas to be contacted with said hydrocarbon feed; passing said hydrocarbon feed, initially surrounded by a helically moving annular blanket of said combustion gases into a reaction zone; therein reacting said hydrocarbon feed by virtue of heat imparted thereto by said combustion gases, to form, predominantly, unsaturated hydrocarbons, and recovering said unsaturated hydrocarbons. The invention provides extremely high yields and throughputs and enables one skilled in the art to effect the cracking of hydrocarbons at higher temperatures and shorter contact times than have heretofore been obtainable. While the process has been described in connection with a now preferred upper temperature of 3500 F., it will be apparent to those skilled in the art that higher temperatures, e. g., approaching 4000" F. can be utilized when suitable refractory materials are available.

I claim:

1. A process which comprises passing a hydrocarbon feed axially into a precombustion zone; passing a combustible mixture comprising a fuel and an oxidant tangentially into said precombustion zone; effecting combustion of said combustible mixture to form combustion gases to be contacted with said hydrocarbon feed; passing said hydrocarbon feed, initially surrounded by a helically moving annular blanket of said combustion gases, into a reaction Zone; therein reacting said'hydrocarbon feed, by virtue of heat imparted thereto by said combustion gases, to form, predominantly, unsaturated hydrocarbons; maintaining the reaction time at a value not substantially greater than that defined by the equation wherein t is the reaction time in seconds and T is the reaction temperature in degrees Rankine, said temperature being in the range of 1760 to 3960" R.; and recovering said unsaturated hydrocarbons.

2. A process which comprises passing a hydrocarbon feed axially into a precombustion zone; passing a combustible mixture comprising a fuel and an oxidant tangentially into said precombustion zone; effecting combustion of said combustible mixture to form combustion gases to be contacted with said hydrocarbon feed; passing said hydrocarbon feed, initially surrounded by a helically moving annular blanket of said combustion gases, into a reaction zone; therein reacting said hydrocarbon feed, by virtue of heat imparted Vthereto by said combustion gases, to form, predominantly, unsaturated hydrocarbons; maintaining the reaction temperature and the reaction time substantially within the limits designated by the area ABCD in Figure 3; and recovering said unsaturated hy' drocarbons,

3. A process according to claim l wherein said hydrocarbon feed is partially cracked prior to passage into said precombustion zone.

4. A process according toclaim 1 wherein steam is present in said combustible mixture.

5. A process according to claim 1 wherein a relatively small proportion of oxygen is added to said hydrocarbon feed prior to introduction into the precombustion Zone.

6. A process for the manufacture of unsaturated hydrocarbons, which process comprises passing a gaseous hydrocarbon stream axially into a rst cylindrical zone having a diameter greater than its length; introducing a combustible fuel gas mixture intorsaid first cylindrical Zone in a direction tangent the inner side walls of said Zone and substantially completely reacting said fuel gas mixture by combustion therein to form combustion gas to be contacted with said hydrocarbon stream; passing combustion gas so formed along an inward spiral path in said first cylindrical zone; passing said combustion gas and said hydrocarbon from said first cylindrical Zone into a second cylindrical Zone having a smaller diameter than, coaxial with, longer than, and adjacent said first cylindrical zone, inl an initial state of annular separation; maintaining said hydrocarbon and said hot cornbustion gas in said second cylindrical Zone in heat exchange relation, whereby said hydrocarbon is heated; regulating said combustion to produce heat in said hot combustion gas to maintain a pyrolysis temperature within the range 1300 to 3500" F.; regulating the reaction time of said hydrocarbon in said second cylindrical zone within a range the upper limit of which is defined by the equation Y. p

10g :tst-12550 and a lower limit defined by the equation 10g (amena-17g() wherein t is the reaction time in seconds and T is the temperature in degrees Rankine; and recovering unsaturated hydrocarbons formed as a product of the process. Y

7. A process for the manufacture of unsaturated hydrocarbons, which process comprises passing a gaseous, predominantly parafiinic hydrocarbon stream axially into the first cylindrical zone having a diameter greater than its length; introducing a combustible fuel gas mixture containing less than Vsufiicient'oxygen for complete combustion thereof into said first cylindrical zone in a direction tangent the inner walls of said zone and substantially completely reacting said fuel gas mixture by combustion therein to form combustion gas to be contacted with said hydrocarbon stream; passing said combustion gas so formed along an inward spiral path in said first cylindrical zone; passing said combustion gas and said hydrocarbon from said first cylindrical zone into a second cylindrical zone having a smaller vdiameter than, coaxial with, longer than, and adjacent said first cylindrical Zone, in an initial state of annular separation; maintaining said hydrocarbon and said combustion gas in said second cylindrical zone in heat exchange relation, whereby said hydrocarbon is heated; regulating said combustion to produce heat in said hot combustion gas to maintain a pyrolysis temperature of said hydrocarbon within the range y1300 to 3500 F.; regulating the contact time of said hydrocarbon in said second cylindrical zone within a range having a lower limit defined by the equation and an upper limit defined by the equation 1 17 600 1 log t) 10.l8 T v wherein t is reaction time in seconds and T is temperature 'in degrees Rankine; withdrawing an effluent from said 17 second' cylindrical zone; and;L rcccv-crina unsaturatcslfhy; drocarbonsvfromrsaid effluent.

8. A process for the manufacture of acetylene, which process comprisesr passing a hydrocarbon containing at least 4 carbon atoms per moleculeaxially into a first cylindrical zone having a diameter greater/than itslength; introducing a combustible fuel gas mixture into said first cylindrical zone in a direction tangentthe inner Walls thereof and substantially, completely reacting said fuel gas mixture by combustion in saidlzone to. forrn combustion gas to be contacted with said hydrocarbon stream; passing said combustion gas so formed along an inward spiral path in said first cylindrical zone; passing saidcombustion gas and said hydrocarbon in an initial state of annular separation from said first cylindricalzoneintoa second cylindrical zone having a smaller diameter than, coaxialwith, longer than, and adjacent said first cylindrical zone; maintaining said hydrocarbon and said combustion gas in said second cylindrical zone in heaty exchange relation, whereby said hydrocarbon is heated; regulating said combustion to maintain a pyrolysis temperature in the range 1700 to '3500e F.; regulating the residence time of said hydrocarbon in, said second cylindrical zone with in a range the upper limit of which is defined by the following equation and the lower limit of which is defined by the equation 1 16,000 g (mes-:T

wherein t is time in seconds and T -is temperature. in degrees Rankine; recoveringancefiiuent fromfsaid second zone; and recovering acetylene from said etliuent.

9. A process for the manufacture` of acetylene2 which process comprises passing a hydrocarbon selected from the group consisting of ethane and propane, axially into a first cylindrical zone having a diameter greater than its length; introducing a combustible fuel gas mixture into said first cylindrical zone in a direction tangent the linner walls thereof and substantially completely reacting said fuel gas mixture by combustion in said zone to "forrricombustion gas to be contacted with said hydrocarbmpassing said combustion gas so formed along an inward spiral path in said first cylindrical zone; passing said combustion gas and said hydrocarbon from said first cylindrical zone into a second cylindrical zone having a smaller diameter than, coaxial with, longer than, and adjacent said first cylindrical zone, in an initial state of annular separation; maintaining said hydrocarbon and said combustion gas in said second cylindrical zone in heat exchange relation, whereby said hydrocarbon is heated; regulating said combustion to maintain a pyrolysis temperature within the range 1700 to 3500 F.; regulating the residence time of said hydrocarbon in said second cylindrical zone within a range the upper limit of which is defined by the equation and the lower limit of which is defined by the equation wherein t is time in seconds and T is temperature in degrees Rankine; recovering an efliuent from said second cylindrical zone; and recovering acetylene from said effluent.

10. A process for the manufacture of acetylene, which process comprises passing a vaporized naphtha axially into a first cylindrical zone having a diameter greater than its length; introducing a combustible fuel gas mixture into said first cylindrical zone in a direction tangent the inner walls of said zone and substantially completely reacting saidfuelgas mixturefbycombzustion in said zone to form combustiqngas `foibe contacted with said vnaphtha; passing saidljcombstiongas'so 'formed along an inward spiral path5 in ysaid,l first 'cylindrical zone; passing combustion gas andvsaid naphtha'fr'om said first cylindrical zone into a second cylindrical zone having a smaller diarneterfthan, coaxial with, longerfthan', aridadjacent said'irs't cylindri-y cal'zone, infaniriitial statefof annular separation; maintainingfsaid" naphtha andfsaid combustion. gas in wsaid secondfcylindrical'zone in heat exchangerelatin, whereby said naphtha isf heatedfregulatin'gfsaid 'combustion tomaintainfa pyrolysis tempraturefin said second vzone in the range i1700 to 3500" Riregulatingth'e residence time of said naphtha in said second yzone within a range the upper limit of which is definedzby the equation and the lower limit. of. which is definedy by the equation per molecule and containinghydrocarbons, boiling below 900. F.; inthevapor phase, axiallyinto a first cylindrical zone having a diameter` greater than itstlength; introducing a combustiblevfueli gas mixturecontaining less` than sufi'icient oxygen for complete combustion 'thereof into said first cylindrical.` zonefin a direction tangentv the inner Walls thereof andA substantially'v completelyv reacting said fuel gas mixturebycombustion in saidvzone, to form combustion gas toV be contactedwith saidhydrocarbon, material; passinghotcombustion gas so frniedalong an inwardfspiral path in. saidfirst cylindricalzone; passing hot combustion gas and said hydrocarbon material in an initial state of.. annularseparation froml saidfirst cylindrical Vzone into a secondfcylindrical. zone having a smaller'diameter. than, coaxial with, longer than, and adjacenty said ffirst cylindrical. zone; maintaining said'hydrocarbon material and', said yhot combustion gas irijsaid second cylindrical zone in heat exchange relation, whereby said hydrocarbon is heated; regulating said combustion to maintain a pyrolysis temperature in said second zone in the range 1300 to 1900 F.; regulating the contact time of said hydrocarbon material in said second zone within a range the upper limit of which is defined by the equation l 12,670 log 5.99 T

and the lower limit of which is defined by the equation wherein t is time n seconds and T is temperature in degrees Rankne; recovering an efiiuent from said second cylindrical zone; and recovering olefins from said effluent` 12. A process for the manufacture of olens, which process comprises passing a hydrocarbon selected from the group consisting of ethane and propane, axially into a first cylindrical zone having a diameter greater than its length; introducing a combustile fuel gas mixture containing less than suliicient oxygen for complete combustion thereof into said first cylindrical zone in a direction tangent its inner side walls and substantially completely reacting said fuel gas mixture by combustion in said zone to form combustion gas to be contacted with said hydrocarbon; passing hot combustion gas so formed along an inward spiral path in said first cylindrical zone; passing hot combustion gas and said hydrocarbon in an initial state of annularseparation from said irst cylindrical zone into a second cylindrical zone having a smaller diameter than, coaxial with, longer than, and adjacent said lirst cylindrical zone; maintaining said hydrocarbon and said hot combustion gas in said second cylindrical Zone in heat exchange relation, whereby said hydrocarbon is heated; regulating said combustion to maintain a pyrolysis temperature in said second zone in the range 1300 to 1900 F.; regulating the contact time of said hydrocarbon in said second zone within a range the upper limit of which is defined by the equation and the lower limit of which vis dened by the equation wherein t is time in seconds and T is temperature in degrees Rankine; removing an effluent from said second cylindrical zone; and recovering oleins from said quenched effluent.

13. A process for the manufacture of oleiins, which process comprises passing a vaporized stream of a predominantly paratiinic naphtha having a boiling range of from 125 to 550 F., axially into a lirst cylindrical zone having a diameter greater than its length; introducing a combustible fuel gas mixture containing less than suicient oxygen for complete combustion thereof into said rst cylindrical zone in a direction tangent the'inner walls thereof and substantially completely reacting said fuel gas mixture by combustion in said zone to form combustion gas to be contacted with said naphtha; passing hot combustion gas so formed along an inward spiral path in said tirst cylindrical zone; passing hot combustion gas and said naphtha in an initial state of annular separation from said rst cylindrical zone into a second cylindrical zone having a smaller diameter than, coaxial with, longer than, and adjacent said first cylindrical zone; maintaining said naphtha and said hot combustion gas in said second cylindrical zone in heat exchange relation, whereby said naphtha is heated; regulating said combustion to maintain a pyrolysis temperature in said second zone vwithin the range 1300 to 1900 F.; regulating the contact and the lower limit of which is defined by the equation 1 17,600 log t) -1030 T wherein t is time in seconds and T is temperature in degrees Rankin; withdrawing an effluent from said second zone; quenching said eiuent; and recovering olefins from said eluent.

14. The process of claim 6 in which said fuel gas mixture contains from to 140 per cent of the amount of oxygen theoretically required for complete combustion thereof.

15. The process of claim 10 in which said fuel gas mixture contains from 50 to 140 percent of the amount of`oxygen theoretically required for complete combustion thereof.

16. The process of claim l0 in which said fuel gas mixture contains from 50 to 140 per cent of the amount of oxygen theoretically required for complete combustion thereof.

17. The process of claim 13 in which said fuel gas mixture contains from to 90 per cent of the amount of oxygen theoretically required for complete combustion thereof. i

18. The process of claim 1 wherein the temperature in said reaction zone is maintained within the range 1700 to 2300 F., and wherein olelins and acetylene are recovered as products.

19. A process according to claim 1 wherein said hydrocarbon feed contains methane and acetylene is recovered as a product of the process.

References Cited in the le of this patent UNITED STATES PATENTS 2,343,866 

1. A PROCESS WHICH COMPRISES PASSING A HYDROCARBON FEED AXIALLY INTO A PRECOMBUSTION ZONE; PASSING A COMBUSTIBLE MIXTURE COMPRISING A FUEL AND AN OXIDANT TANGENTIALLY INTO SAID PRECOMBUSTION ZONE; EFFECTING COMBUSTION OF SAID COMBUSTIBLE MIXTURE TO FORM COMBUSTION GASES TO BE CONTACTED WITH SAID HYDROCARBON FEED; PASSING SAID HYDROCARBON FEED, INITIALLY SURROUNDED BY A HELICALLY MOVING ANNULAR BLANKET OF SAID COMBUSTION GASES, INTO A REACTION ZONE; THEREIN REACTING SAID HYDROCARBON FEED, BY VIRTUE OF HEAT IMPARTED THERETO BY SAID COMBUSTION GASES, TO FORM, PREDOMINANTLY, UNSATURATED HYDROCARBONS; MAINTAINING THE REACTION TIME AT A VALUE NOT SUBSTANTIALLY GREATER THAN THAT DEFINED BY THE EQUATION 